Various carriers have been developed in order to deliver substances of interest such as drugs to cells. Particularly, when the substances of interest are bacterial cell components such as a cell-wall skeleton (CWS) fraction of Mycobacterium Bovis bacillus Calmette-Guerin (BCG), strong immunostimulatory activity is expected. These bacterial cell components, however, are insoluble in water and are therefore difficult to formulate into forms applicable to organisms. Another problem of the bacterial cell components is low interaction with cells due to their large molecular weights and negative chargeability. Accordingly, carriers containing surfactants, lipid membrane structures, and the like have been proposed as carriers for the bacterial cell components. For example, a preparation for cancer immunotherapy comprising a bacterial cell component, an oil substance, a surfactant, and a stabilizer (Patent Literature 1) has been disclosed. In addition, the present inventors have disclosed a liposome comprising a bacterial cell component in a lipid membrane (Patent Literature 2).